The present invention relates to a circuit for separating luminance signals/color signals (hereinafter referred to as "the Y/C separating circuit") in a television receiver of a NTSC system, and more particularly to the Y/C separating circuit which is simplified in constitution by using only a line memory and is suitable for the digitization of video signals, and which changes the bandwidth of the filter in accordance with the signals by use of the filter utilizing the horizontal and vertical correlation of video signals, thereby to improve resolution and the signal-to-noise ratio.
Recently, since the integration degree of an integrated circuit(IC) has improved, the digital signal processing can be performed economically. Accordingly, a digital type television(hereinafter referred to as "TV") can get to compete with an analog type TV in both price and function because reason the digital type TV makes it possible to perform the various signal processing methods which are impossible to perform in the analog type TV.
In a conventional color TV with an analog or digital signal processing system, the 1H type comb filter shown in FIG. 1 or the 2H type comb filter shown in FIG. 2 is used to separate the luminance/color signal from the composite video signal, thereby providing much improvement of picture quality over prior color TV. However, there still remains a problem of the deterioration in picture quality due to inaccuracy of the Y/C signal separation. Heretofore, there have been disclosed three-dimensional digital signal processing techniques in which the frame memory is used. However, these techniques have problems in which the constitution of the circuit becomes very complicated requires large scale memory and the price of the product become high.